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January 20, 2012

Autism Chances Enhanced With Low Birth Weight

by editor

The basis of autism spectrum disorder (ASD) is long known to have a strong genetic component, however new research is suggesting that environmental factors may play an equally important role in this developmental disorder affecting nearly one in 100 children.

The study, published in the journal Psychological Medicine suggests that low birth weight is an important environmental factor contributing to the risk of ASD, reports Wendy Leopold for Northwestern University.

Lead author of the study, Molly Losh, who teaches and conducts research in Northwestern University´s School of Communication says, “Our study of discordant twins -- twin pairs in which only one twin was affected by ASD -- found birth weight to be a very strong predictor of autism spectrum disorder.”

Previous studies of twin have shown that when one identical twin had ASD, the other twin was much more likely to have ASD than not explains Losh, “Because identical twins share virtually 100 percent of their genes, this is strong evidence for the role of genetics in autism. Yet it is not 100 percent the case that ASD affects both identical twins in a twin pair.”

“That only one twin is affected by ASD in some identical twin pairs suggests that environmental factors may play a role either independently or in interaction with autism risk genes,” UPI reports.

Losh continued, “And because autism is a developmental disorder impacting brain development early on, it suggests that prenatal and perinatal environmental factors may be of particular importance.”

The findings of the researchers add to an increasing base of knowledge about the complex causes of autism. Low birth weight continues to show up as a key feature that interacts with underlying genetic predisposition to autism.

The researchers studied a population-based sample of 3,725 same-sex twin pairs that were part of the Swedish Twin Registry´s Child and Adolescent Twin Study that was directed by Paul Lichtenstein of Sweden´s Karolinska Institute.

The discordant twins they studied were pairs in which one twin was more than about 14 ounces or at least 15 percent heavier at birth than the other.